Credits & Attributions

Cerebra is built with the following open-source and openly-licensed works.

Software libraries

• D3.js v7 — ISC License, © Mike Bostock. d3js.org
• TopoJSON Client v3 — ISC License, © Mike Bostock. github.com/topojson
• Tone.js — MIT License, © Yotam Mann & contributors. tonejs.github.io
• Flubber v0.3.0 — MIT License, © Noah Veltman. github.com/veltman/flubber
• three.js r185.1 — MIT License, © three.js authors. Powers the 3D molecule viewer in the chemistry lessons. threejs.org

Coding platform (computers section)

• Pyodide (CPython for WebAssembly), core distribution — Mozilla Public License 2.0, © Pyodide contributors. Powers the in-browser Python engine. pyodide.org
• wasm-clang (a clang/LLVM toolchain compiled to WebAssembly) — Apache License 2.0, © WebAssembly Community Group participants. The bundled LLVM binaries (clang, lld) and C/C++ standard library are licensed Apache 2.0 with the LLVM exception. Powers the in-browser C and C++ engines. github.com/binji/wasm-clang

Fonts

• Nunito — SIL Open Font License 1.1, © The Nunito Project Authors.
• Share Tech Mono — SIL Open Font License 1.1, © Carrois Apostrophe.

Audio

• Salamander Grand Piano samples — CC BY 3.0, by Alexander Holm (packaged via the midi-js-soundfonts project). CC BY 3.0
• Acoustic piano samples (88-note set) — from the midi-js-soundfonts project (MIT), served from static/core/audio/piano/. [[ OUTSTANDING: confirm whether this 88-note set is the MusyngKite or the FluidR3_GM rendering, and credit that soundfont’s own terms here. The files themselves do not say, so this cannot be settled from the repository. ]]

Maps & geographic data

• Natural Earth vector data (country/state boundaries) — public domain, packaged as TopoJSON via the world-atlas / us-atlas projects (ISC). naturalearthdata.com
• Natural Earth admin-1 states & provinces (1:10m) — the province, state, and federal-subject outlines behind the subdivision quizzes for Canada, China, Greenland, India, Mexico and Russia. Filtered to those countries and simplified into static/core/geo/admin1-<ISO3>.json, one file per country. Natural Earth places all its map data in the public domain: “no permission is needed to use Natural Earth. Crediting the authors is unnecessary,” and it may be used freely in commercial products — we credit it here regardless. Source: nvkelso/natural-earth-vector, terms of use.
• Natural Earth lakes (1:10m) — the Great Lakes, drawn as water over the Canadian provinces and North American mainland maps (static/core/geo/great-lakes.json). Neither atlas above carries lakes — both run the boundary down the middle of the water — so the five lakes plus Lake St. Clair are laid over the finished map, islands and all. Public domain, same source as above.
• Historical world borders — the 24 year-by-year boundary snapshots behind the History Atlas (static/core/geo/historical/world_*.geojson) come from the historical-basemaps project by André Ourednik and contributors, licensed under the GNU General Public License v3.0. The full license text ships alongside the data at static/core/geo/historical/LICENSE.txt. Those files — and the History Atlas boundary shapes derived from them — remain available to you under GPL-3.0. Cerebra’s own application code is a separate work and is not placed under that license by using this data.

A note on disputed areas: map data inevitably encodes political claims. Where a source reflects de-facto control rather than international recognition, Cerebra follows international recognition. Crimea and Sevastopol are carried in Natural Earth’s Russian admin-1 set but stamped with Ukrainian ISO codes; they are excluded from the Russian federal-subject quizzes accordingly.

Science data

• Periodic table of the elements — the table behind the chemistry Elements lessons (static/core/js/pt_elements.js) is Cerebra’s own compilation, written from scratch; no third-party dataset, library, or image was used. Element names, symbols and standard atomic weights follow the definitions published by the International Union of Pure and Applied Chemistry (IUPAC), credited here with thanks — those are facts about nature rather than creative work, and carry no licence conditions. Where spelling differs by region, Cerebra shows the American form and accepts the IUPAC form too.

Anatomy

• Human skeleton, anterior view — the drawing behind the biology Bones lessons (static/core/anatomy/skeleton_anterior.svg) is public domain, from Wikimedia Commons, by Mikael Häggström, derived from an image by Mariana Ruiz Villarreal (User:LadyofHats). Both released it into the public domain and no attribution is required; this credit is given with thanks. Cerebra’s copy regroups the drawing so each bone is a single addressable element and re-emits the path data at lower precision — the artwork itself is unchanged.
• Human brain, lateral view — the drawing behind the biology The Brain lessons (static/core/anatomy/brain_lateral.svg) is public domain, from Wikimedia Commons, by User:Mysid. Released into the public domain with no attribution required; credited here with thanks. Cerebra’s copy drops the label leader lines — they pointed straight at the parts the quiz asks you to name — and groups the six regions; the artwork itself is unchanged.
• 3D skeleton, brain, muscle, heart, liver, digestive and urinary models — the models the in 3D lessons render (static/core/anatomy/models/) are derived from BodyParts3D, the whole-body anatomical model published by the Database Center for Life Science (Research Organization of Information and Systems, Japan). Used under the Creative Commons Attribution 4.0 International licence, which asks for this credit:
  “BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International”
  Cerebra’s copies are modified: the meshes belonging to one structure are welded together, simplified to a triangle budget the browser can draw, re-normalled, and re-encoded in a compact binary form; the axes and units are converted to the ones the rest of the site uses. Nothing is sculpted or added — every surface is the original scan at lower resolution.
• 3D whole-body nervous system model (static/core/anatomy/models/nervous-body.*) — its nerves, plexuses, spinal dura and skeleton are adapted from Z-Anatomy, the libre 3D atlas of anatomy by Gauthier Kervyn and Marcin Zielinski, itself built on BodyParts3D; its brain and eyes are BodyParts3D, credited above. Used under the Creative Commons Attribution-ShareAlike 4.0 International licence:
  “Z-Anatomy – The libre 3D atlas of anatomy – CC-BY-SA 4.0” and “BodyParts3D – The Database Center for Life Science”
  Cerebra’s copy is modified: the nerve curves are turned into tubes, grouped by nerve, simplified, re-encoded, and placed onto the BodyParts3D skeleton’s coordinates. This adapted model is itself shared under CC BY-SA 4.0, as that licence requires. Parts of Z-Anatomy that came from non-commercial or unlicensed sources (its inner ear and its brain) are not used.
• 3D cell and organelle models (static/core/anatomy/models/cell-* and closeup-*) — adapted from OpenOrganelle, the volume electron microscopy data of the COSEM and CellMap Project Teams, HHMI Janelia Research Campus (datasets jrc_hela-2, jrc_hela-3, jrc_mus-liver and jrc_ctl-id8-2). Used under the Creative Commons Attribution 4.0 International licence. Described in Xu et al., Nature 599, 147–151 (2021) and Heinrich et al., Nature 599, 141–146 (2021).
  Cerebra’s copies are modified: the meshes are simplified, named, coloured and re-encoded; chromatin and the nucleolus are rebuilt as smoothed solids; and in the T-cell model the nuclei are separated into the cancer cell’s and the T cells’.

Flags

• Country & territory flag images (all 252 PNGs served from static/core/flags/, self-hosted) — downloaded 2026-07-18 from Flagpedia.net via its FlagCDN service (320-pixel PNG set, ISO 3166 codes). Flagpedia offers these images free of charge for any commercial or non-commercial use without attribution required; this credit is provided with thanks. The underlying national flag designs are public domain.

Full license texts are included with the source in NOTICES.md.